Methods of Removing Particles From Over Semiconductor Substrates

ABSTRACT

Some embodiments include methods of removing particles from over surfaces of semiconductor substrates. Liquid may be flowed across the surfaces and the particles. While the liquid is flowing, electrophoresis and/or electroosmosis may be utilized to enhance transport of the particles from the surfaces and into the liquid. In some embodiments, temperature, pH and/or ionic strength within the liquid may be altered to assist in the removal of the particles from over the surfaces of the substrates.

TECHNICAL FIELD

Methods of removing particles from over semiconductor substrates.

BACKGROUND

Semiconductor fabrication is utilized for construction of, for example,integrated circuitry (IC) and microelectromechanical systems (MEMS). Thefabrication comprises formation of numerous devices and structures, andoften comprises deposition and removal of materials to patternstructures into desired shapes.

Particles may occur during the deposition and removal of materials, andsuch particles may interfere with the performance of devices.Accordingly, it is desired to remove the particles. Fabricationprocesses will often comprise multiple stages dedicated to rinses,megasonic agitation, and/or other conventional methods for particleremoval.

Although substantial effort is expended to remove particles, problemsassociated with the particles persist. Accordingly, it is desired todevelop new approaches for removing particles from semiconductorsubstrates.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 are a diagrammatic cross-sectional side view, and topview, respectively, of a semiconductor substrate that may be utilized insome example embodiments.

FIG. 3 is a diagrammatic, cross-sectional side view of a semiconductorsubstrate that may be utilized in some example embodiments.

FIG. 4 is a view of the semiconductor substrate of FIG. 3 being exposedto a flowing liquid to remove particles.

FIGS. 5 and 6 show the semiconductor substrate of FIG. 3 being treatedwithin a system; and specifically being exposed to an electrical field,as well as to flowing liquid, to remove particles in accordance with anexample embodiment. The processing stage of FIG. 6 is subsequent to thatof FIG. 5.

FIGS. 7 and 8 are diagrammatic, cross-sectional side views of a regionof a system being utilized to treat a semiconductor substrate with anelectrical field and a flowing liquid to remove particles in accordancewith another example embodiment. The processing stage of FIG. 8 issubsequent to that of FIG. 7.

FIG. 9 is a diagrammatic, cross-sectional side view of a region of anapparatus being utilized to treat a semiconductor substrate with anelectrical field and a flowing liquid to remove particles in accordancewith another example embodiment.

FIG. 10 is a diagrammatic, cross-sectional side view of a region of anapparatus being utilized to treat a semiconductor substrate with anelectrical field and a flowing liquid to remove particles in accordancewith another example embodiment.

FIG. 11 is a diagrammatic, cross-sectional side view of a region of anapparatus being utilized to treat a semiconductor substrate with anelectrical field and a flowing liquid to remove particles in accordancewith another example embodiment.

FIG. 12 is a diagrammatic, three-dimensional view of a region of anapparatus being utilized to treat a semiconductor substrate with anelectrical field and a flowing liquid to remove particles in accordancewith another example embodiment.

FIG. 13 is a diagrammatic, cross-sectional side view of a region of anapparatus being utilized to treat a semiconductor substrate with anelectrical field and a flowing liquid to remove particles in accordancewith another example embodiment.

FIG. 14 is a diagrammatic, cross-sectional side view of a region of anapparatus being utilized to treat a semiconductor substrate with anelectrical field and a flowing liquid to remove particles in accordancewith another example embodiment.

FIGS. 15-17 are graphical illustrations of dynamic changes intemperature, pH and ionic strength, relative to time, that may occur insome example embodiments.

FIG. 18 is a graph showing a relationship between interaction forces andparticle radii for Van der Waals forces, and showing hydrodynamic forcesthat may be imparted on particles of varying radii.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

In some embodiments, new methods for removing particles from oversemiconductor substrates utilize electrokinetic forces to assist intransferring the particles into a flowing liquid, whereby the particlesmay be swept away by hydrodynamic flow forces. The electrokinetic forcesmay utilize one or both of electrophoresis (i.e., movement of chargedparticles in an electric field) and electroosmosis (i.e., movement ofliquid in an electric field). In some embodiments, electrokinetic forcesmay be utilized to overcome Van der Waals forces, to assist indislodging particles from a substrate.

The utilization of electrokinetic forces may provide advantages overutilization of hydrodynamic forces alone. For instance, utilization ofelectrokinetic forces may reduce cleaning times. Further, inconventional methods that utilize hydrodynamic forces there is often anaggressive mechanical aspect of the cleaning. Such aggressive aspect isutilized to enhance dislodgment of particles from a semiconductorsubstrate surface, and may, for example, comprise exposure of thesubstrate to high-amplitude megasonic energy for a substantial durationof time. The aggressive mechanical aspect may damage sensitivestructures of a semiconductor substrate. The utilization ofelectrokinetic forces may enable the aggressive mechanical aspect to beomitted, or to be reduced in aggressiveness and/or duration.

Example aspects of the invention are described with reference to FIGS.1-17.

Referring to FIGS. 1 and 2, such illustrate an example semiconductorsubstrate 10 in cross-sectional side view (FIG. 1) and top view (FIG.2), respectively. Substrate 10 may comprise any suitable semiconductormaterial, or combination of semiconductor materials, and may, forexample, comprise, consist essentially of, or consist of, for example,monocrystalline silicon lightly-doped with background p-type dopant. Theterms “semiconductive substrate,” “semiconductor construction” and“semiconductor substrate” mean any construction comprisingsemiconductive material, including, but not limited to, bulksemiconductive materials such as a semiconductive wafer (either alone orin assemblies comprising other materials thereon), and semiconductivematerial layers (either alone or in assemblies comprising othermaterials). The term “substrate” means any supporting structure,including, but not limited to, the semiconductive substrates describedabove.

Semiconductor substrate 10 may comprise various materials, layers andstructures (not shown) associated with IC and/or MEMS fabrication.

Semiconductor substrate 10 is shown having a pair of opposing primarysurfaces 12 and 14, with the primary surfaces appearing planar in thediagrammatic views of FIGS. 1 and 2. During IC and/or MEMS fabrication,multiple structures may be formed over a semiconductor substrate, andsuch structures may lead to a non-planar topography across one or bothof the primary surfaces. However, the primary surfaces may still beconsidered to be generally horizontal, and the non-planar topography maybe considered a minor local permutation across the generally horizontalprimary surfaces. Thus, in some embodiments a semiconductor wafer may bereferred to as having a horizontal primary surface, and such referenceis not to be interpreted as meaning that the surface has an absolutelyplanar topography.

FIG. 3 diagrammatically illustrates a semiconductor construction 16, andmay be considered to represent a zoomed-in view of a region of substrate10 at a processing stage utilized in fabrication of IC and/or MEMS. Thesubstrate 10 has a trench 18 extending therein, and the upper surface 12of substrate 10 extends along an undulating topography that includes thetrench.

A plurality of particles 20, 22, 24 and 26 are shown along the uppersurface 12, with particle 22 being shown within the trench.

Referring to FIG. 4, construction 16 is placed within a system 25. Thesystem 25 is configured to enable a liquid 28 to be flowed across thesurface 12 of substrate 10. The liquid 28 is flowed along a directionindicated by arrows 29, 31, 33, 35 and 37. Differences in lengths of thearrows are utilized to indicate differences in the speed of flow. Theliquid 28 has a bulk fluid flow above a boundary layer 30. The fluidflow attenuates within the boundary layer 30, and decreases to static ornearly static (in other words, little or no flow) immediately adjacentsubstrate surface 12. The reduction in the rate of fluid flow in regionsadjacent surface 12 relative to other regions of the fluid is due tofluid flow dynamics, and is generally present to some degree when fluidis flowed across a static substrate.

An interface of the boundary layer 30 with the bulk fluid flow region ofliquid 28 is diagrammatically illustrated in FIG. 4 with a dashed line41. The boundary layer has a thickness between surface 12 and interface41. Such thickness may vary depending on the topography of surface 12,the rate of flow of liquid 28, and the turbulence within the flowingliquid. However, turbulence may lead to damage to structures present ona substrate 10, and thus it may be desired to keep the liquid flow to aspeed which does not induce excessive turbulence. The boundary layerthickness may be greater than or equal to about one micron, and may begreater than or equal to several microns for some hydrodynamic flowconditions. In some applications, the thickness of the boundary layermay be reduced to hundreds of nanometers through acoustic streamingtechnologies.

The trench 18 represents a valley in the undulating topography ofsurface 12, and such valley is a deep region within boundary layer 30.Unless liquid 28 flows with high velocity, and associated highturbulence, the liquid flow will have little impact on particles trappedwithin the valleys in the undulating topography.

In operation, the flowing liquid may interact with large particles thatextend to a height well above the boundary layer 30 to sweep suchparticles away from upper surface 12 of substrate 10. In contrast, theflowing liquid has little impact on the particles that are too small toextend above the boundary layer (such as the particles 20 and 26), orthat are trapped within valleys in the undulating topography of surface12 (such as the particle 22 trapped with trench 18). Thus, particle 24is most effectively removed, relative to the other particles, because ithas a diameter larger than the boundary layer. Particles 20 and 26 aremore difficult to remove because only a percentage of the bulk flowvelocity is available within the boundary layer. Trench particle 22 willbe the most difficult to remove.

When IC and MEMS were formed of relatively large-dimension structures,it was only relatively large particles that were of concern and thatneeded to be removed. As IC and MEMS are formed to increasingly smallerdimensions, smaller particles are becoming of concern. The particlesthat are presently of concern may have dimensions of less than 50nanometers, and accordingly may be too small to penetrate above theinterface 41 of the boundary layer.

Two problems may occur with particles that are too small to penetratethrough the interface 41 of the boundary layer 30. The first may be thatthe flowing liquid 28 will not dislodge the particles unless the liquidflows with enough force to introduce substantial turbulence in theliquid. The second problem may be that, even if particles are dislodgedfrom the surface, the particles may take a substantial duration of timeto pass through the boundary layer and into the bulk flow region ofliquid 28. Specifically, the particles dislodged from the surface 12 ofsubstrate 10 may undergo a “random walk” through the boundary layerwhich can increase the duration of a cleaning cycle. Also, the particlesmay redeposit onto the substrate instead of passing out of the boundarylayer and into the bulk flow region of the liquid.

Some methods which can overcome the first problem are to introduceadditional mechanical forces along the boundary between the particlesand the surface 12 of substrate 10. Such additional mechanical forcesmay include momentum transfer from spray and/or from megasoniccavitation. Another method used to attempt to overcome the first problemcomprises chemical modification of surface 12 and/or the particles tocreate forces that assist in repelling the particles from the surface.Even if methods to overcome the first problem are successful, the secondproblem may still exist. Particles which may be particularly problematicto remove with flowing liquid (either alone or with additionalmechanical forces), and which may be problematic for IC and/or MEMSfabrication, are particles having a maximum cross-sectional dimension ofless than or equal to 100 nanometers, such as, for example, particleshaving maximum cross-sectional dimensions of from about 10 nanometers toabout 100 nanometers.

FIGS. 5 and 6 show the system 25 modified in accordance with an exampleembodiment. The modified system includes a pair of electrodes 32 and 34on horizontally opposing sides of semiconductor construction 16. Theelectrodes are connected to one another through a power source 36 whichis configured to apply a voltage differential between the electrodes.FIG. 5 shows system 25 prior to a voltage differential being applied tothe electrodes, and FIG. 6 shows system 25 after a voltage differentialhas been applied to the electrodes.

The system 25 at the processing stage of FIG. 6 has an electric fieldset up between electrodes 32 and 34 due to the voltage differential ofthe electrodes relative to one another. An arrow 38 is used to indicatea direction of electrophoretic movement of charged particles. Theelectrical field is perpendicular to a primary horizontal surface ofsubstrate 10, and is of appropriate polarity relative to particles 20,22, 24 and 26 that it electrophoretically pushes the particles towardelectrode 34. The electric field thereby assists in dislodging theparticles from the surface 12 of substrate 10. In the shown embodiment,the particles move from a positive electrode to a negative electrode. Inother embodiments, the electrodes may be reversed, and the particles maymove from the negative electrode toward the positive electrode. In thisillustration, the particle is positively charged, and will move towardthe negative electrode. In another embodiment, a negatively chargedparticle could be directed to move toward a positive electrode.

The electrophoretic force on the particles transports the particlesthrough boundary layer 30 and into the bulk flow part of liquid 28,whereupon the particles can be swept away from substrate 10. Themovement of particles 20, 22, 24 and 26 is diagrammatically illustratedin FIG. 6 by arrows 40, 42, 44 and 46, respectively.

In some embodiments, liquid 28 may be considered to have a thicknessacross the surface 12 of the substrate 10, and across the particles 20,22, 24 and 26. A first region of the thickness of the liquid may beconsidered to be near substrate 10, and to correspond to boundary region30; while a second region of the thickness of the liquid is more distantfrom the substrate than the first region, and has more flow than thefirst region. The electric field is imparted across the surface 12 ofthe substrate and across the particles 20, 22, 24 and 26, and isutilized to enhance transport of the particles from the first region ofthe liquid (the boundary region) to the second region liquid (the morerapidly flowing region, or, in other words, the bulk flow region).

The voltage differential applied between plates 32 and 34 may be anysuitable differential to dislodge the particles, and may, for example,correspond to a differential anywhere between 0.1 volts and theelectrolysis threshold of liquid 28. The actual voltage differentialutilized may be tailored for particular sizes of particles havingparticular surface charges, in a particular liquid (having a particularionic strength, a particular temperature, and a particular pH), andrelative to a substrate 10 having a surface 12 carrying a particularcharge. The charges on the surfaces of the particles and/or the chargeon the surface 12 of the substrate may be modified by providingadditives (such as surfactants) within the liquid 28, as discussedbelow. Also, one or more of the temperature, ionic strength and pH maybe modified during the electrophoresis, as discussed below.

The voltage differential between plates 32 and 34 may be applied withdirect current and/or with alternating current. An advantage ofutilizing direct current is that such may allow electrophoretic forcesto be directed in a desired direction for a duration long enough totransport particles entirely through the boundary layer 30 and into thebulk flow region of liquid 28. In contrast, an advantage of utilizingalternating current is that such may enable a rocking motion of theparticles to be achieved, which may assist in dislodging the particles.Further, alternating current may provide a magnetic field in addition tothe electric field, and such magnetic field may assist in dislodgingsome types of particles.

In some embodiments, the advantages of both alternating current anddirect current are utilized sequentially. Specifically, an alternatingcurrent is first applied to “rock” the particles and initiate theprocess of dislodging the particles, and then direct current is appliedto transport the particles through a boundary layer and into a bulk flowregion of a liquid. In such embodiments, an electric field may beconsidered to be provided for a duration; and the field may beconsidered to be maintained with alternating current for an initial partof the duration, and to then be maintained with a direct current for asubsequent part of the duration. In some embodiments, AC and DC may beapplied simultaneously, with the AC component riding on a fixed DCcomponent.

FIGS. 7 and 8 show the system 25 modified in accordance with anotherexample embodiment. A different portion of the semiconductorconstruction 16 is shown in FIGS. 7 and 8 than was shown in FIGS. 3-6.Specifically, the region of semiconductor construction 16 shown in FIGS.7 and 8 has a planar portion of surface 12, and has particles 60, 62 and64 over such planar portion. The arrows 29 and 31 (FIG. 7) are not shownin FIG. 8 due to a lack of room in FIG. 8, but the flow of liquid 28 inthe boundary region 30 of FIG. 8 may match that of the liquid in theboundary region of FIG. 7 in some embodiments.

The system of FIGS. 7 and 8 includes a pair of electrodes 52 and 54 onlaterally opposing sides of semiconductor construction 16. Theelectrodes are connected to one another through a power source 56 whichis configured to apply a voltage differential between the electrodes.FIG. 7 shows system 25 prior to a voltage differential being applied tothe electrodes, and FIG. 8 shows system 25 after a voltage differentialhas been applied to the electrodes.

The system 25 at the processing stage of FIG. 8 has an electric fieldset up between electrodes 52 and 54 due to the voltage differential ofthe electrodes relative to one another. Such electric field isdiagrammatically illustrated with a positive charge shown on electrode54, and a negative charge shown on electrode 52. The electrical field isparallel to a primary horizontal surface of substrate 10. The electricfield creates electroosmosis within the static boundary region 30 of theliquid, as illustrated by positive (+) and negative (−) chargesaccumulating within boundary region 30 adjacent the electrodes 52 and54, respectively. The location of the charges within the boundary layerare diagrammatically illustrated in the figure. In actual applications,the charges may be part of an electric double layer, with a primarycomponent of the charges being due to ions absorbed on the surface 12 ofthe substrate.

The electric field causes ions to migrate within the boundary region 30,which induces electroosmosis. Such electroosmosis (water movement) maycreate forces on the particles 60, 62 and 64, which may assist indislodging the particles from the surface 12 of substrate 10. The forcesmay result from, for example, the particles 60, 62 and 64 beingdrawn/repelled relative to the charged regions. As another example, themigrating ions are surrounded by hydration spheres as they migrate sothat there is hydrodynamic flow associated with the migration of theions, and such hydrodynamic flow may dislodge the particles 60, 62 and64.

The movement of the particles imparted by the electroosmosis mayovercome Van der Waals forces to release the particles from thesubstrate, whereupon other forces (for instance electrophoretic forces)may transport the particles through boundary layer 30 and into the bulkflow region of liquid 28. In some embodiments, the electroosmosis mayrock the particles to assist in dislodging the particles from surface12, and then other forces may be utilized to transport the particlesthrough the boundary layer and into the bulk flow region of the liquid.Horizontal, or rocking, movement of particles 60, 62 and 64 isdiagrammatically illustrated in FIG. 8 by arrows 70, 72 and 74,respectively; and flow of the particles 60, 62 and 64 isdiagrammatically illustrated by arrows 76, 78 and 80, respectively.

The voltage differential applied between plates 52 and 54 may be anysuitable differential to create electroosmosis, and may, for example,correspond to a differential anywhere between 0.1 volts and theelectrolysis threshold of liquid 28. The actual voltage differentialutilized may be tailored for particular sizes of particles, havingparticular surface charges, in a particular liquid (having a particularionic strength, a particular temperature, and a particular pH), andrelative to a substrate 10 having a surface 12 carrying a particularcharge. The charges on the surfaces of the particles and/or the chargeon the surface 12 of the substrate may be modified by providingadditives (such as surfactants) within the liquid 28, as discussedbelow. Also, one or more of the temperature, ionic strength and pH maybe modified during the electroosmosis, as discussed below.

The voltage differential between plates 52 and 54 may be applied withdirect current or with alternating current. In some embodiments, bothalternating current and direct current may be utilized; with thealternating and direct currents being applied sequentially relative toone another.

The electrophoresis discussed with reference to FIGS. 5 and 6 may beutilized entirely independently of the electroosmosis discussed withreference to FIGS. 7 and 8, so that some embodiments employ onlyelectrophoresis, and other embodiments employ only electroosmosis.Alternatively, the electrophoresis and electroosmosis may be utilizedsynergistically with one another. For instance, the electroosmosis maybe utilized to start the movement of the particles by rocking theparticles along a horizontal axis and thereby disrupting Van der Waalsand/or other forces retaining the particles to the substrate.Subsequently, electrophoresis may be utilized to lift the particles fromthe substrate and transport them through a boundary region and into abulk flow region of a liquid. In embodiments in which bothelectroosmosis and electrophoresis are utilized, the electroosmosis andelectrophoresis may be simultaneous relative to one another, or may besequential relative to one another.

Any suitable apparatus may be utilized for the electrophoresis andelectroosmosis discussed above with reference to FIGS. 5-8. Some exampleapparatuses are illustrated in FIGS. 9-14.

FIG. 9 shows a system 90 configured for utilization of electrophoresisto assist in removal of particles. Similar numbering will be used todescribe FIG. 9 as was utilized above in describing FIGS. 1-8, whereappropriate.

System 90 includes a bath of liquid 28 retained within a vessel 92. Thevessel has an inlet 94 and an outlet 96 so that the liquid 28 may becontinuously flowed through the vessel during utilization of the liquidto remove particles. The flow of the liquid is diagrammaticallyillustrated with arrows 95.

A semiconductor substrate 10 is retained within the vessel between apair of electrodes 32 and 34. The substrate and electrodes may beretained in the shown orientation with one or more support structures(not shown).

The electrodes 32 and 34 are electrically connected to a power source36. In operation the power source is utilized to create a voltagedifferential between the electrodes 32 and 34 in a manner discussedabove with reference to FIGS. 5 and 6.

System 90 is illustrated to also comprise a mechanism for impartingsonic energy into the liquid 28. The mechanism is diagrammaticallyillustrated as comprising a megasonic transducer 98 along the bottom ofvessel 92, and a power source 99 coupled to the megasonic transducer. Inoperation, the power source may cause high-frequency agitation ofmegasonic transducer 98 which can then impart megasonic energy to liquid28. The utilization of megasonic energy may enhance removal of particlesin some embodiments. In other embodiments, the mechanism for impartingsonic energy may be omitted. In the shown embodiment, the semiconductorsubstrate 10 is a wafer extending parallel to a megasonic transducer 98;in other embodiments, the wafer may extend perpendicular to themegasonic transducer.

FIG. 10 shows another example system (100) configured for utilization ofelectrophoresis to assist in removal of particles. Similar numberingwill be used to describe FIG. 10 as was utilized above in describingFIGS. 1-9, where appropriate.

The system 100 of FIG. 10, like the system 90 of FIG. 9, comprises thevessel 92 having the inlet 94 and outlet 96. Such vessel may be utilizedfor achieving flow of liquid 28 across a semiconductor substrate 10.However, system 100 of FIG. 10 differs from the system 90 of FIG. 9 inthat the system 100 utilizes a conductive upper material 102 ofsemiconductor substrate 10 in place of the electrode 32 of system 90.Specifically, the conductive upper material 102 and electrode 34 areconnected to one another through a power source 36, and in operation thepower source creates an electric field between the upper material 102and electrode 34.

The system of FIG. 10 may be utilized in applications in which asemiconductor substrate has a conductive upper material, such as, forexample, applications in which a conductive upper material is formedduring fabrication of IC devices. The conductive upper material maycomprise, for example, one or more of various metals (for instance,platinum, tungsten, titanium, tantalum, etc.), metal-containingcompositions (for instance, metal nitrides, metal silicides, etc.), andconductively-doped semiconductor materials (for instance,conductively-doped silicon, conductively-doped germanium, etc.).

FIG. 11 shows a system 110 configured for utilization of electroosmosisto assist in removal of particles. Similar numbering will be used todescribe FIG. 11 as was utilized above in describing FIGS. 1-8, whereappropriate.

System 110 includes a liquid 28 flowing across a semiconductor substrate10. The flow of the liquid is diagrammatically illustrated with arrows115.

System 110 includes electrodes 52 and 54 of the type described abovewith reference to FIGS. 7 and 8. However, unlike FIGS. 7 and 8, theelectrodes of FIG. 11 are above substrate 10 rather than being onopposing lateral sides of substrate 10. Thus, an electric fieldgenerated between the electrodes 52 and 54 is across a portion of wafer10 rather than across an entirety of wafer 10, which reduces the amountvoltage needed to maintain a given field. The electrodes 52 and 54 maybe connected to one another through a power source (not shown in FIG.11) analogous to the power source 56 of FIGS. 7 and 8.

Electrodes 52 and 54 are connected to a support mechanism 112 which isconfigured to move the electrodes laterally (diagrammaticallyrepresented by arrow 113), and vertically (diagrammatically illustratedby arrow 115). Also, substrate 10 is supported by a mechanism 114configured to rotate the substrate (diagrammatically represented byarrow 117). In operation, the substrate may be rotated by mechanism 114,and the electrodes may be moved by mechanism 112, so that the electrodesare passed over an entirety of an upper surface of the substrate. Thus,the entire upper surface may be exposed to electroosmosis createdbetween electrodes 52 and 54 to assist in removal of particles from overthe upper surface of substrate 10.

FIG. 12 shows another system (120) configured for utilization ofelectroosmosis to assist in removal of particles. Similar numbering willbe used to describe FIG. 12 as was utilized above in describing FIGS.1-8, where appropriate.

System 120 is a modified liquid-spray apparatus. A semiconductorsubstrate 10 is retained within a plurality of clamps 122, 124, 126 and128; and a nozzle 130 is provided over the substrate and configured tospray liquid onto the substrate (the spray of the liquid is representedby arrows 131). The nozzle may be configured to be moved relative to thesubstrate (the movement of the nozzle is represented by arrow 133)and/or the substrate may be configured to be moved relative to thenozzle (the movement of the substrate is represented by arrow 135).

The clamps 122, 124, 126 and 128 are arranged in sets of opposing pairs;with clamps 122 and 126 being in opposing relation to one another, andwith clamps 124 and 128 being in opposing relation one another. Opposingclamps 122 and 126 are connected to a power source 140 which may beutilized to establish an electric field between claims 122 and 126; andsimilarly opposing clamps 124 and 128 are connected to a power source142 which may be utilized to establish an electric field between claims124 and 128. In some embodiments, the same power source may be utilizedto establish an electric field between multiple opposing pairs ofclamps, rather than using the multiple power source configuration shownin FIG. 12. Also, in some embodiments there may be only a singleopposing pair of clamps that is utilized to generate an electric field,or there may be more than the shown two opposing pairs of clampsutilized to generate electric fields. The electric fields generatedbetween different sets of opposing pairs of clamps may be formedsimultaneously with one another, or sequentially relative to oneanother; and may utilize one or both of alternating current and directcurrent.

In operation, an electric field is generated across a substrate 10utilizing one or more opposing pairs of clamps, and such field createselectroosmosis to assist in transporting particles from a surface ofsubstrate 10 into the liquid projected across the surface with the spraynozzle 130.

FIG. 13 shows a system 150 that may be utilized for electrophoreticallytreating a batch of semiconductor substrates. The apparatus includesmultiple electrodes 152, 154 and 156 coupled to a power source 158.Although three electrodes are shown, in other embodiments there may beother numbers of electrodes; and although only one power source isshown, in other embodiments there may be multiple power sources.

Semiconductor substrates 160 and 162 are retained between adjacent pairsof electrodes by support structures (not shown). In operation, liquid isflowed along primary surfaces of the substrates (the liquid flow isdiagrammatically illustrated with arrows 155), and electric fields areformed between adjacent pairs of electrodes (the electric fields arerepresented by showing positive (+) and negative (−) charges on theelectrodes). The semiconductor substrates and electrodes may be within abath of liquid, analogous to the bath described with reference to FIG.9, with the liquid flowing through the bath and across the surfaces ofthe substrates.

The system of FIG. 13 forms electric fields orthogonal to the primarysurfaces of the semiconductor substrates, and thus is configured forutilizing electrophoresis to assist in transporting particles into theflowing liquid. The system may be modified to also provide electricfields parallel to the primary surfaces of the semiconductor substratesso that the system may also utilize electroosmosis to assist intransporting particles into the flowing liquid. FIG. 14 shows system 150modified to comprise a pair of electrodes 164 and 166 along the opposinglateral surfaces of the semiconductor substrates 160 and 162 so that thesystem may utilize both electroosmosis and electrophoresis to assist intransporting particles into a flowing liquid (not shown in FIG. 14). Theelectrodes 164 and 166 are connected to one another through a powersource 168, with such power source being suitable to create the electricfield between the electrodes 164 and 166.

In some embodiments, the removal of particles may be enhanced byaltering surface properties of the substrate, surface properties ofparticles, and/or properties of a rinsing solution (with the “rinsingsolution” being the liquid flowed across a semiconductor substrateduring particle removal).

One method of altering surface properties of the substrate and/orparticles is to provide additives within the rinsing solution; with theadditives being suitable to modify surfaces of at least some ofparticles and/or to modify surfaces of a semiconductor substrate. Theadditives may be provided to a concentration of from about 0.001 weightpercent to about 1 weight percent. Example additives are surfactants.The surfactants may be any surfactants suitable to modify properties ofparticle surfaces and/or substrate surfaces, and may, for example,include anionic surfactants, nonionic surfactants, cationic surfactants,and ampholytic surfactants; including, but not limited to, surfactantsavailable from Dow chemical as TRITON™, TERGITOL™, DOWFAX™ and ECOSURF™materials.

Methods of altering properties of the rinse solution may includemodification of pH, ionic strength and/or temperature. Some embodimentsinclude dynamically altering a rinse solution during utilization of therinse solution. The dynamic alteration may comprise methods discussed inU.S. patent application Ser. No. 12/136,661; and may comprise alterationof any of numerous properties of the solution, including, for example, atemperature of the solution, a pH of the solution, and/or concentrationsof one or more components of the solution. FIGS. 15-17 graphicallyillustrate dynamic alteration of temperature, pH, and ionic strength,respectively.

Referring to FIG. 15, a graph 200 comprises an x-axis corresponding totime, and a y-axis corresponding to temperature. A curve 202 shows thevariation of the temperature of a rinse solution with time, andspecifically shows that the temperature is continuously variable over aperiod of time. In other words, the temperature is non-static over theperiod time, as opposed to reaching a static equilibrium. The showncurve corresponds to a temperature gradient. The curve may be consideredto comprise multiple iterations of a process in which the temperaturegoes between values 204 and 206.

The low temperature 204 and high temperature 206 may differ from oneanother by at least about 30° C., and in some embodiments may differfrom one another by at least about 60° C. For instance, the lowtemperature 204 may correspond to about room temperature (23° C.), andthe high temperature 206 may correspond to about 90° C.

The time for each iteration from a low temperature to a hightemperature, and back, may be any suitable duration; and may be, forexample, at least a few seconds in embodiments in which the lowtemperature and high temperature differ from one another by at leastabout 30° C.

The curve 202 is shown to be continuously variable during the entireduration illustrated in graph 200. The fluctuation of the temperaturebetween the low and high temperatures may be referred to as temperaturesweeping. At some point the temperature sweeping may be ceased, and thesubstrate exposed to a static, equilibrium, temperature. Such may beaccomplished by flowing a static temperature rinse solution across thesubstrate.

The temperature sweeping may provide benefits during the rinsing of asubstrate and utilization of electrokinetic forces. For instance, thetemperature sweeping may enhance kinetics of reactions in someembodiments, and may inhibit kinetics of reactions in other embodiments.As another example, the magnitude of electrostatic interaction betweenparticles and an electric field may be influenced by temperature in someembodiments, and in such embodiments the temperature sweeping mayenhance rocking of particles when the particles are exposed to anelectric field.

Referring to FIG. 16, a graph 210 comprises an x-axis corresponding totime, and a y-axis corresponding to pH. A curve 212 shows the variationof the pH of a rinse solution with time, and specifically shows that thepH is continuously variable over a period of time. In other words, thepH is non-static over the period of time, as opposed to reaching astatic equilibrium. The shown curve corresponds to a pH gradient. Theexample curve may be considered to comprise multiple iterations of aprocess in which the pH goes between values 214 and 216.

The low pH 214 and high pH of 216 may differ from one another by five ormore pH units, and in some embodiments may differ from one another byeight or more pH units. For instance, the low pH 214 may correspond to 2(or another suitable acidic pH), and the high pH 216 may correspond to10 (or another suitable basic pH).

The time for each iteration from a low pH to a high pH, and back, may beany suitable duration; and may be, for example, at least a few seconds.

The curve 212 is shown to be continuously variable during the entireduration illustrated in graph 210. The fluctuation of the pH between thelow and high pH's may be referred to as pH sweeping.

The pH sweeping may provide benefits during the rinsing of a substrateand utilization of electrokinetic forces. For instance, the pH sweepingmay alter surface charges of the particles to enhance electrostaticcoupling between an electric field and the particles, and therebyenhance removal of the particles. As another example, the pH sweepingmay alter the surface charges of both the substrate and the particles tocreate electrostatic repulsion between the particles and the substrate.

Referring to FIG. 17, a graph 220 comprises an x-axis corresponding totime, and a y-axis corresponding to ionic strength. A curve 222 showsthe variation of the ionic strength within a rinse solution with time,and specifically shows that the ionic strength is continuously variableover a period of time. In other words, the ionic strength is non-staticover the period time, as opposed to reaching a static equilibrium.

The shown curve corresponds to a concentration gradient. The curve maybe considered to comprise multiple iterations of a process in which theionic strength fluctuates between values 224 and 226.

The low concentration 224 and high concentration 226 may differ from oneanother by several fold, and in some embodiments may differ from oneanother by one or more orders of magnitude.

The time for each iteration from a low ionic strength to a high ionicstrength, and back, may be any suitable duration; and may be, forexample, at least three seconds.

The curve 222 is shown to be continuously variable during the entireduration illustrated in graph 220. The fluctuation of the ionic strengthbetween the low and high ionic strengths may be ceased at some point,and the substrate exposed to a static, equilibrium, ionic strength.

The alteration of ionic strength may provide benefits during the rinsingof a substrate and utilization of electrokinetic forces. For instance,the alteration of ionic strength may alter the zeta potential of theparticles to thereby enhance electrostatic coupling of the particleswith an electric field.

FIG. 18 shows interaction forces as a function of particle size forsilicon oxide particles on a silicon oxide surface, and specificallyindicates that Van der Waals adhesion forces are orders of magnitudelarger than the hydrodynamic force for typical flows that can bedirected onto the center of a particle. For at least this reason,alternate removal forces, such as those discussed herein areadvantageous to dislodge nanoparticles from surfaces. In compliance withthe statute, the subject matter disclosed herein has been described inlanguage more or less specific as to structural and methodical features.It is to be understood, however, that the claims are not limited to thespecific features shown and described, since the means herein disclosedcomprise example embodiments. The claims are thus to be afforded fullscope as literally worded, and to be appropriately interpreted inaccordance with the doctrine of equivalents.

1. A method of removing particles from over a surface of a semiconductorsubstrate, comprising: flowing a liquid across the surface and theparticles; and while the liquid is flowing, utilizing one or both ofelectrophoresis and electroosmosis to enhance transport of the particlesfrom the surface and into the liquid.
 2. The method of claim 1 whereinliquid comprises additives suitable to modify surfaces of at least someof the particles, the additives being present within the liquid to aconcentration of from about 0.001 weight percent to about 1 weightpercent.
 3. The method of claim 2 wherein the additives includesurfactants.
 4. The method of claim 2 wherein the additives includeions.
 5. The method of claim 1 wherein electrophoresis is utilized. 6.The method of claim 5 further comprising dynamically altering atemperature of the liquid across a range of at least about 30° C. duringthe utilization of the electrophoresis.
 7. The method of claim 5 furthercomprising dynamically altering a pH of the liquid across a range of atleast about 5 pH units during the utilization of the electrophoresis. 8.The method of claim 1 wherein electroosmosis is utilized.
 9. The methodof claim 8 further comprising dynamically altering a temperature of theliquid across a range of at least about 30° C. during the utilization ofthe electroosmosis.
 10. The method of claim 8 further comprisingdynamically altering a pH of the liquid across a range of at least about5 pH units during the utilization of the electroosmosis.
 11. The methodof claim 1 wherein both electroosmosis and electrophoresis are utilized.12. The method of claim 11 wherein the electroosmosis andelectrophoresis are utilized sequentially relative to one another. 13.The method of claim 11 wherein the electroosmosis and electrophoresisare utilized simultaneously.
 14. A method of removing particles fromover a surface of a semiconductor substrate, comprising: flowing aliquid across the surface and the particles, the liquid having thicknessover the substrate, a first region of the thickness being near thesubstrate and being relatively static, a second region of the thicknessbeing further from the substrate than the first region and having moreflow than the first region; while the liquid is flowing, imparting anelectric field across at least a region of the surface; and wherein theelectric field causes forces on the particles which enhance transport ofthe particles from the first region to the second region.
 15. The methodof claim 14 wherein: the electric field is provided for a duration; andthe electric field is maintained with an alternating current for atleast part of the duration.
 16. The method of claim 14 wherein: theelectric field is provided for a duration; and the electric field ismaintained with direct current for at least part of the duration. 17.The method of claim 14 wherein: the electric field is provided for aduration; the electric field is maintained with an alternating currentfor part of the duration; and the electric field is maintained with adirect current for another part of the duration.
 18. The method of claim14 wherein the semiconductor substrate has a primary horizontal surface,and wherein at least a majority of the electric field is orientedparallel to said primary horizontal surface.
 19. The method of claim 14wherein the semiconductor substrate has a primary horizontal surface,and wherein at least a majority of the electric field is orientedperpendicular to said primary horizontal surface.
 20. A method ofremoving particles from over semiconductor substrate surfaces,comprising: exposing the surfaces having the particles thereon toflowing liquid and to an electric field; wherein the electric fieldcauses forces on the particles which enhance transport of the particlesfrom the semiconductor substrate surfaces into the liquid; and utilizingthe flowing liquid to sweep the particles away from the surfaces. 21.The method of claim 20 wherein the semiconductor substrate surfaces arecomprised by a single semiconductor substrate, and wherein: thesubstrate has a pair of opposing primary surfaces, one of the primarysurfaces being a top surface and the other being a bottom surface; thesubstrate is provided between a pair of electrodes; the electrodes areutilized to provide at least a portion of the electric field to benormal to the primary surfaces of the semiconductor substrate; and theliquid is flowed across at least one of the primary surfaces of thesemiconductor substrate.
 22. The method of claim 21 wherein thesemiconductor substrate surfaces are subjected to sonic energy duringthe utilization of the electric field.
 23. The method of claim 20wherein the semiconductor substrate surfaces are comprised by a singlesemiconductor substrate, and are electrically conductive regions, andwherein: the substrate has a pair of opposing primary surfaces, one ofthe primary surfaces being a top surface and the other being a bottomsurface; the top surface comprising the electrically conductive regions;the substrate is beneath an electrode; a voltage difference is providedbetween the electrically conductive regions of the top surface and theelectrode, and is utilized to provide at least a portion of the electricfield to be normal to the primary surfaces of the semiconductorsubstrate; and the liquid is flowed across the top surface of thesemiconductor substrate.
 24. The method of claim 20 wherein thesemiconductor substrate surfaces are comprised by a batch ofsemiconductor substrates, and wherein: the semiconductor substrates areretained in a bath, and are spaced from one another; electrodes areprovided within the spaces between the semiconductor substrates and areutilized for providing at least a portion of the electric field to benormal to primary surfaces of the semiconductor substrates; and theliquid is flowed within the spaces between the semiconductor substrates.25. The method of claim 20 wherein the semiconductor substrate surfacesare part of a single semiconductor substrate, and wherein: thesemiconductor substrate is retained within a spray cleaning apparatuswith clamps provided around a periphery of the substrate; the liquid issprayed onto the substrate with a nozzle of the spray cleaningapparatus; and at least part of the electric field is provided with avoltage differential applied between a pair of the clamps.
 26. Themethod of claim 25 wherein the voltage differential is providedutilizing alternating current.
 27. The method of claim 25 wherein thevoltage differential is provided utilizing direct current.
 28. A methodof removing particles from surfaces of a plurality semiconductorsubstrates, comprising: placing the semiconductor substrates within abath of flowing liquid; while the semiconductor substrates are withinthe bath, exposing the semiconductor substrate surfaces to varyingconditions which include one or more of continuously varyingtemperature, continuously varying ionic strength, and continuouslyvarying pH; and while the semiconductor substrate surfaces are exposedto the varying conditions, imparting at least one electric field to thesurfaces; the electric field enhancing transport of particles from thesurfaces into the liquid.
 29. The method of claim 28 wherein thesemiconductor substrates are exposed to continuously varying pH whilethe semiconductor substrates are within the bath.
 30. The method ofclaim 28 wherein the semiconductor substrates are exposed tocontinuously varying temperature while the semiconductor substrates arewithin the bath.
 31. The method of claim 28 wherein the semiconductorsubstrates are exposed to continuously varying ionic strength while thesemiconductor substrates are within the bath.
 32. The method of claim 28wherein the at least one electric field induces electrophoresis to causeforces on the particles, with such forces being primarily perpendicularto primary surfaces of the substrates.
 33. The method of claim 28wherein the at least one electric field induces electroosmosis to causeforces on the particles, with such forces being primarily parallel toprimary surfaces of the substrates.